Repair_Monitoring_Wells_Questions_Set_2.pdf

Repair Monitoring Wells Questions Set 2

1) Section 33 23 00 Part 3.1 States that "The well shall be constructed according to the rules for Water Well construction in the state of Montana." Montana law states that any water well must have steel casing grouted to at least 25' below ground level with no perforations above that level, however Montana does not regulate dewatering wells. The dewatering well cross section calls for 10' of blind casing, which again is perfectly legal as the state does not regulate dewatering wells.

Section 33 23 00 Part 4.4.3 Grouting, calls for the well to be grouted according to Montana State regulations, but asks for the grout top to end at 10'. Does Malmstrom wish to keep their own 10' specs or conform to Montana's 25' spec? If Malmstrom does choose to adhere to Montana Water Well specs the maximum screen length would need to be lowered to 65' in a 100' deep well to allow for the last 10' of slotted pipe. Can Malmstrom clarify the blind casing and grout depth?

Malmstrom wants to keep the 10’ specification. The blind casing and grout should be 10’.

2) The Dewatering Well Cross Section Drawing calls for 6" Johnson PVC Vee-Wire 0.040" slotted well screen. Section 33 23 00 Part 3.5 calls for a minimum of 70' of 6" Stainless Steel well screen. Can the contracting agency clarify if they want PVC or Stainless Steel well screen?

Due to collapse pressures, I would highly recommend stainless steel. The depth range for these wells is stated to be between 50' and 100'. Can we adjust these screen lengths to account for shallow depths and or adjusted grout levels?

The drawings are correct and the 6” PVC well screen is what is wanted. Well screen lengths would be adjusted to shallow depths, keep grout levels the same. It is anticipated that these five wells will be 100’ being they are next to the launch tube.

3) The Dewatering Well Cross Section Drawing on the right side near the middle states "The last 10' of well casing shall be 6" schedule 40 PVC" Then on the lower right of the drawing it states, "Evenly distribute 3/8" minus clean gravel around bottom 10' of slotted steel pipe." Can you clarify whether this 10' slotted tail pipe is constructed of PVC, black steel or galvonized steel? Can you also clarify that this 10' tail pipe shall be saw slotted and utilize a 3/8" minus gravel filter pack for this section only?

The 10’ tail pipe shall be 6” schedule 40 PVC. The 3/8” minus clean gravel pack will be just around the bottom 10’ of casing.